Index: trunk/test/unit/org/openstreetmap/josm/testutils/annotations/OsmApi.java
===================================================================
--- trunk/test/unit/org/openstreetmap/josm/testutils/annotations/OsmApi.java	(revision 18821)
+++ trunk/test/unit/org/openstreetmap/josm/testutils/annotations/OsmApi.java	(revision 18821)
@@ -0,0 +1,80 @@
+// License: GPL. For details, see LICENSE file.
+package org.openstreetmap.josm.testutils.annotations;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+import java.util.Map;
+
+import org.junit.jupiter.api.extension.AfterEachCallback;
+import org.junit.jupiter.api.extension.BeforeAllCallback;
+import org.junit.jupiter.api.extension.BeforeEachCallback;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.junit.jupiter.api.extension.ExtensionContext;
+import org.junit.platform.commons.support.ReflectionSupport;
+import org.junit.runners.model.InitializationError;
+import org.openstreetmap.josm.io.OsmApiInitializationException;
+import org.openstreetmap.josm.io.OsmTransferCanceledException;
+import org.openstreetmap.josm.spi.preferences.Config;
+import org.openstreetmap.josm.testutils.FakeOsmApi;
+
+/**
+ * Used for setting the desired OsmApi type
+ */
+@BasicPreferences
+@ExtendWith(OsmApi.OsmApiExtension.class)
+@HTTP
+@LayerManager
+@Retention(RetentionPolicy.RUNTIME)
+@Target({ElementType.TYPE, ElementType.METHOD})
+public @interface OsmApi {
+    APIType value() default APIType.NONE;
+    enum APIType {
+        /** Don't use any API */
+        NONE,
+        /** Use the {@link org.openstreetmap.josm.testutils.FakeOsmApi} for testing. */
+        FAKE,
+        /** Enable the dev.openstreetmap.org API for this test. */
+        DEV
+    }
+
+    class OsmApiExtension implements BeforeAllCallback, BeforeEachCallback, AfterEachCallback {
+        @Override
+        public void afterEach(ExtensionContext context) throws Exception {
+            Config.getPref().put("osm-server.url", "http://invalid");
+            ((Map<?, ?>) ReflectionSupport.tryToReadFieldValue(
+                    org.openstreetmap.josm.io.OsmApi.class.getDeclaredField("instances"), null)
+                    .get()).clear();
+        }
+
+        @Override
+        public void beforeAll(ExtensionContext context) throws Exception {
+            this.beforeEach(context);
+        }
+
+        @Override
+        public void beforeEach(ExtensionContext context) throws Exception {
+            final APIType useAPI = AnnotationUtils.findFirstParentAnnotation(context, OsmApi.class)
+                    .map(OsmApi::value).orElse(APIType.NONE);
+            // Set API
+            if (useAPI == APIType.DEV) {
+                Config.getPref().put("osm-server.url", "https://api06.dev.openstreetmap.org/api");
+            } else if (useAPI == APIType.FAKE) {
+                FakeOsmApi api = FakeOsmApi.getInstance();
+                Config.getPref().put("osm-server.url", api.getServerUrl());
+            } else {
+                Config.getPref().put("osm-server.url", "http://invalid");
+            }
+
+            // Initialize API
+            if (useAPI != APIType.NONE) {
+                try {
+                    org.openstreetmap.josm.io.OsmApi.getOsmApi().initialize(null);
+                } catch (OsmTransferCanceledException | OsmApiInitializationException e) {
+                    throw new InitializationError(e);
+                }
+            }
+        }
+    }
+}
Index: trunk/test/unit/org/openstreetmap/josm/testutils/annotations/TestUser.java
===================================================================
--- trunk/test/unit/org/openstreetmap/josm/testutils/annotations/TestUser.java	(revision 18821)
+++ trunk/test/unit/org/openstreetmap/josm/testutils/annotations/TestUser.java	(revision 18821)
@@ -0,0 +1,63 @@
+// License: GPL. For details, see LICENSE file.
+package org.openstreetmap.josm.testutils.annotations;
+
+
+import static org.junit.jupiter.api.Assumptions.assumeTrue;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+import java.net.Authenticator;
+import java.net.PasswordAuthentication;
+
+import org.junit.jupiter.api.extension.AfterEachCallback;
+import org.junit.jupiter.api.extension.BeforeAllCallback;
+import org.junit.jupiter.api.extension.BeforeEachCallback;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.junit.jupiter.api.extension.ExtensionContext;
+import org.openstreetmap.josm.TestUtils;
+import org.openstreetmap.josm.data.UserIdentityManager;
+import org.openstreetmap.josm.io.auth.CredentialsManager;
+import org.openstreetmap.josm.spi.preferences.Config;
+import org.openstreetmap.josm.tools.Utils;
+
+/**
+ * Used for tests that require a test user to be defined via -Dosm.username and -Dosm.password.
+ * This uses the {@link OsmApi.APIType#DEV} server.
+ */
+@BasicPreferences
+@OsmApi(OsmApi.APIType.DEV)
+@ExtendWith(TestUser.TestUserExtension.class)
+@Retention(RetentionPolicy.RUNTIME)
+@Target({ElementType.TYPE, ElementType.METHOD})
+public @interface TestUser {
+    class TestUserExtension implements BeforeAllCallback, BeforeEachCallback, AfterEachCallback {
+        @Override
+        public void afterEach(ExtensionContext context) throws Exception {
+            UserIdentityManager.getInstance().setAnonymous();
+            CredentialsManager.getInstance().purgeCredentialsCache(Authenticator.RequestorType.SERVER);
+        }
+
+        @Override
+        public void beforeAll(ExtensionContext context) throws Exception {
+            this.beforeEach(context);
+        }
+
+        @Override
+        public void beforeEach(ExtensionContext context) throws Exception {
+            assumeTrue(TestUtils.areCredentialsProvided(),
+                    "OSM DEV API credentials not provided. Please define them with -Dosm.username and -Dosm.password");
+            final String username = Utils.getSystemProperty("osm.username");
+            final String password = Utils.getSystemProperty("osm.password");
+            assumeTrue(username != null && !username.isEmpty(), "Please add -Dosm.username for the OSM DEV API");
+            assumeTrue(password != null && !password.isEmpty(), "Please add -Dosm.password for the OSM DEV API");
+            Config.getPref().put("osm-server.auth-method", "basic");
+
+            // don't use atomic upload, the test API server can't cope with large diff uploads
+            Config.getPref().putBoolean("osm-server.atomic-upload", false);
+            CredentialsManager.getInstance().store(Authenticator.RequestorType.SERVER, org.openstreetmap.josm.io.OsmApi.getOsmApi().getHost(),
+                    new PasswordAuthentication(username, password.toCharArray()));
+        }
+    }
+}